1. Field of the Invention
The present invention relates to a numerical controller and, more specifically, to a numerical controller capable of instructing a plurality of axes using a single instruction.
2. Description of the Related Art
There is a numerical controller that drives a plurality of motors, drives the table and machining machine via a ball screw, and positions the workpiece and tool in a desired position. Such a numerical controller needs to make control so as to position the workpiece and tool in a desired position by instructing the motors about their operation.
When the motors are instructed to perform different types of operation, switching between instruction circuits has been performed based on the setting of the instruction program. In such a technique, when the number of control axes is increased, it is necessary to add an instruction program and install an additional instruction cable and instruction circuit.
FIG. 17 is a schematic view showing the structure of a numerical controller of the prior art, in which a servo driving apparatus 40 is connected to a numerical controller 20. A plurality of servo motors 50 are connected to the servo driving apparatus 40 and each servo motor 50 is driven by the corresponding axis instruction transmitted from the numerical controller 20.
In addition, an upper level controller 30 is connected to the numerical controller 20. The upper level controller 30 includes a plurality of pulse generator 32a, 32b, 32c, and 32d corresponding to the number of servo motors 50 and a plurality of control signal generators 34a and 34b. Of the plurality of pulse generators 32a, 32b, 32c, and 32d, the pulse generator 32a is connected to an input channel 1CH of the numerical controller 20, the pulse generator 32b is connected to an input channel 2CH of the numerical controller 20, the pulse generator 32c is connected to an input channel 3CH of the numerical controller 20, and the pulse generator 32d is connected to an input channel 4CH of the numerical controller 20.
There are a number of control signal generators 34a and 34b in association with the number of types of signals to be controlled. Since the types of signals to be controlled are two (signal 1 and signal 2) in the example shown in FIG. 17, two control signal generators 34a and 34b are provided. A number of (four in this example) pulse cables corresponding to the number of servo motors 50 run from each of the control signal generators 34a and 34b and are connected to the numerical controller 20 so that independent instructions are provided for the servo motors, respectively.
Japanese Patent Application Laid-Open No. 10-340106 discloses a technique (similar to the prior art technique above) for selecting a command from commands stored in a motion control module and providing an instruction for the control apparatus of each axis.
The numerical controller of the prior art technique above includes a number of pulse generators 32a, 32b, 32c, and 32d and pulse cables corresponding to the number of servo motors 50. Accordingly, when different servo motors 50 are instructed to provide different instructions for the axes, the instruction program and instruction circuit need to be changed. When the number of axes and the number of servo motors 50 that drive the axes are increased, the corresponding instruction cables and instruction circuits need to be added.